Charging mechanism for an enclosure



Jan- 19, i969 c. c. wALTERs 2,921,699

CHARGING MECHANISM FOR AN ENcLosURE ATTORNEYS Jan. 19, 1960 c. c.wALTERs CHARGING MECHANISM FOR AN ENCLOSURE 6 Sheets-Sheet 2 Filed April4, 1957 .u iii? INVENTOR. CLAEENCE C. WALTEES A TENE YS WQ Q NS mm. WQum mm. gif i I i I l l l l I l l l I l I Il.. HJ. vw wm www@ vm @n Jan.19, 1960 Filed April 4, 1957 WINI (o) c. c. wALTERs 2,921,699

CHARGING MECHANISM FOR AN ENCLOSURE 6 Sheets-Sheetv 25v INVENToR.

CLARENCE C. WAL 716,95

BY v 2% fag@ @MM f Mm Jan. 19, 1960 c. c. wALTERs 2,921,699

CHARGING MECHANISM FOR AN 'ENcLosuRE Filed April 4, 1957 '6 Sheets-Sheet4 n HIWHIRQ TTOE/VEYS Jan. 19, 1960 c. c. wALTERs v 2,921,699

CHARGING MECHANISM FOR-AN ENcLosURE Filed April 4, i957 6 Sheets-Sheet 594 A 58 57 INVENTOR. i @M25/vas c. wA/ es T By A 7' TOENE YS Jan. 19,1960 c. c. wALTERs 2,921,699

CHARGING MECHANISM FOR AN ENCLOSURE Filed Aprilv 4, 1957 6 Sheets-Sheet6 INVENTOR. CZAEEA/CE C. WALTEES m: Vm\v PN@ mm.

BY 17,9%, w?, zm 0mm A TTO/ENEYS United States Patent CHARGING MECHANISMFOR AN ENCLOSURE Clarence C. Walters, Willoughby, Ohio, assignor toRepublic Steel Corporation, Cleveland, Ohio, a corporation of New JerseyApplication April 4, 1957, Serial No. 650,793

12 Claims. (Cl. 214-1) This invention relates to novel and improvedmeans for charging elongated members such as rods, bars, rails, or thelike into an enclosure having an opening in the end thereof. By way ofexempliiication, and not of limitation, it will be illustrated anddescribed with reference to the feeding of elongated rods or barsthrough an openv ing in the end wall of what is conventionally termed arod mill.

Those skilled in the art of grinding and crushing material are familiarwith the construction and operation of a rod mill. Briefly, it comprisesa drum-like enclosure of substantial size having means for rotating iton a xed horizontal axis. ln one embodiment in connection with which thepresent invention has been successfully practiced, the enclosure isabout sixteen feet long, and about ten feet in diameter and the bars tobe inserted in the enclosure are slightly shorter than the length of theenclosure, and are about six inches in diameter.

The material to be ground, for example fragments of ore an inch or lessin greatest dimension, is fed into the enclosure which contains a numberof cylindrical bars lying loosely in the bottom thereof. The enclosureis rotated at a speed such that the material and the bars areintermingled and tumbled. In a practical application, taconite oredischarged from ,Crushers is conveyed to the feed end of the yrotatingmill and ground product issues from the discharge end, and maythereafter be screened, the oversize pieces being returned to the4 feedend.

The material to be ground is often of extreme hardness, such as taconiteore for example, and evenfthough hardened steel rods are used, the rodswear away rather rapidly and must be periodically replaced. Normallyworn rod pieces are self ejecting, moving out with the ground material,so that the mill may -be maintained in continuous operation with just ashort pause for the graphs which can be readily brought to chargingposition for operation, and removed therefrom when not needed, and whichis provided with safety control means rendering it operative only whenit is properly aligned in the aforesaid charging position.

VOther objects and advantages will be apparent from a study of thefollowing description, in conjunction with Vthe accompanying drawingsillustrating one exempliiication of the invention, wherein:

Fig. 1 is a top plan view of an assembly comprising a rod mill, acomminuted material distributor, rod charging means, and rod loadingmeans for delivering individual rods to the charging means.

Fig. 2 is a side elevational view of the assembly shown in Fig. l, butwith the rod loading means omitted.

Fig. 3 is an end elevational view as seen from the left end of Fig. l,but not showing the rod mill itself.

Fig. 4 is a top plan view, with parts broken away, showing `the fixedframe portion for the charging device on a somewhat larger scale thanshown in Fig. l.

Fig. 5 is a top plan View showing the movable carriage Y portion for thecharging device, but with motors omitted.

charging operation to be later described. The apparatus t to bedescribed, can, of course, be used to charge any elongated element intoany open-end enclosure, and those skilled in the art will -at oncerealize that heat treating or annealing furnaces can be charged inthemanner hereinafter illustrated and described.

An object of the present invention is to provide charging means having aportion insertible longitudinally into an open ended enclosure, saidportion carrying thereon yan elongated element to be discharged withinthe enclosure, and further carrying thereon additional means forejecting said element.

A further object of the invention is -to provide means as defined in thelast preceding paragraph which can be operated even though the enclosureis being rotated on an axis substantially co-incident with the nsertibleportion of the charging means, if the operation within the enclosure issuiiciently quiescent to permit insertion of 4the charging means. In rodmills it is usually advisable to operate the charging device when themill is at rest.

neath collars 21 and 22, y-being 4supported on piers 23 I'his carriageis reciprocable endwise towards the right on the xed frame of Fig. 4. y

Fig. 6 is a side elevational view of the carriage of Fig. 5 assembled inthe frame of Fig. 4.

Fig. 7 is a sectional view, further enlarged, taken on the plane of line7 7 of Fig. 6.

Fig. 8 is a side elevational view taken on the line 8 8 of Fig. 3, buton a somewhat larger scale.

Figs. 9, 10 and 11 are detailed vertical sectional views, somewhatenlarged, taken respectively on the planes of the lines 9 9, 10-10, and11 11 of Fig. 6.

Figs. 12, 13, 14 and l5 are detailed vertical sectional views, somewhatenlarged, taken respectively on the planes of the lines 12 12, 13 13,14-14 and 15 15 of Fig. 5.

' IFig. 16 is a side elevational view showing details of the framelocking mechanism, as seen from the location of the line 116 16 of Fig.9.

Y Fig. 17 is a detail view of the traction chain securing means.

Y Fig. 18 is an electric wiring diagram showing the control system forthe charging device, some parts being indicated schematically.

General v description Speaking first generally, to identify the mainelements comprising the invention and other elements collaboratingtherewith, there is shown in Figs. 1 and 2 a rod mill 20. The mill isrotatable in bearings (not shown) beand 24. Located axially throughcollar 22 is a port through which ore is delivered to mill 20. Water isadded when wet grinding. At the left end of the mill is a so-calledsplitter 25 which in the present instance divides the ground product ofthe mill to chutes representedV by the broken line elements 26 and 27,the prodluct being thereby carried to further comminuting units such asball mills, magnetic separators, or the like.

For the purpose of this description it will be noted that although theground material passes outwardly through an aperture in the left end ofmill 20, and into splitter 25, Vthis left end of the mill and thesplitter provide an axial vopening indicated by broken lines 28 in Fig.2, said opening having adequate clearance to admit the movablecarriage'29 (Figs. l and 5) whereby rods are charged into the mill.Reference will therefore hereinafter be made to the rod-chargingaperture as referring to the axial one between'lines 28 vand 29 as seenin Fig. 2. At the right end of theY mill,- within vfixed peripheralguard housing 30, is a rotating means Vcomprising a kring gear frame .37carried on legs 3S. The frame 37 Vand carriage n 29 are clearly shown intop plan view in Figs. 4 and 5 respectively.

The rod loading rack 39 is a convenient accessory butis not an essentialpart of the invention. lt consists of a body and driven by a pinion 'i Aconventional driving motor f ansiantaasY fixed stand having `verticallegs which `support a pair of spaced, slightly'inclined beams 4t? and 41on'which are stacked a supply of rods 42. A rodrelease mechanism whichdeliversV one rodat a tint as desired, is operated by hand wheel Itallows a rod to roll on to carriage 29, and one rod 42 Vis shown onV thecarriage in Figs. l and 2. p

' The charger frame 47 supportedY by four legs 38 at its ends and theselegs are braced by cross members 48 (Figs. 9 and l1). f Legs 3S havefeet 30a which rest on the platform, and each Y foot is provided with adownwardly extending pin 38b which is insertible through a respectivelocating` hole 'in the platform to align the charging device in workingrelationship to the rod mill.

Channel members 46,- 47 carry respective angle iron track supports 49and Si) which in turn supporttlpper tracks or rails 51 and 52 (Figs. 9,10 and 1l). These tracks and their supports extendsubstantially the.full length of the frame 37 and they provide a runway for the 'Wheels44 of carriage 29.k Subsidiary lower track members 53 and 54 areprovided on the under side of channels 46and 47 and they affordstabilizing tracks for a pair of carriage wheels (Figs. 6, 7 and 8)which run thereunder to prevent up-ending of the left end of thecarriage when it is extended to its maximum distance for- 'Y wardly,namely to the right in Figs. l', 2 and 6.

The carriage The carriage 29 (Fig. 5) Ycomprises `a pair of .inwardlyconcave structural steel channel members 57 and 58 spaced and bracedboth by occasional cross piecesV 59 (Figs. 9, 12 and 14) and also bythevariousV transverse Y yaxles 6i) which carry wheels 44. The axles arefree t0 rotate in suitable bearing, packing,land retaining assemblies inthe channel members 57 and 58 in any suitable y manner not herenecessary to describe.

,'Ihere are two actual-driving axles, one 60a (FigsgS .and 8) for thelower or stabilizing wheels 45 and another 60b'(-Figs. 5 and 6) for themain carriage drive.

- .engages a sprocket 72 on an intermediate shaft 73 (Fig.

.7). Shaft 73 through meshed gears 74, 75 drives the .stabilizing axle76 which carries stabilizing wheels 45 hereinabove referred to.

i, i Y Y., The carriage drivev *Y .The main carriage drive (Figs. 5, 6and 14) is Yfrom i and through a horizontal sprocket chain 79 toasprocket lower ledges of tracks 51 and 52. These link chains have forsimplicity been omitted from most of the drawings. They provide novnslip traction for driving axle 60b.

It is now apparent that forward and reverse rotation of reversible motor62 produces suitable movement of carriage 29. By reason of thestabilizing effect of wheels 45, the carriage can be extended inwardlyfrom frame 3 7 a quite substantial distance into mill 2t?, as indicatedby the broken line showing 29 Within the mill in Fig. 2. Safety limitswitches stop the carriage lat a predetermined limit of travel in bothdirections, as will be explained later in connection with the wiringdiagram, Fig. 18.

When carriage V29 reaches its furthest extent of movement into `mill 29,it ejectsand drops the Yrod carried thereon by means now to bedescribed. i

YThe ejectol' roll driveV The carriage carries a number of rollers 61hereinabove mentioned. Each roller has a recessed or notched peripheryto receive and retain a rod 42 when placed thereon bythe rod loader. Theframe carries inclined cover platesV 84 and 85 to prevent rods fromfalling down between the carriage and the frame. Each roller is lixed toa' sleeve 86 which in turn is pinned to a rotatable shaft S7. There areeight rollers, best shown in Fig. 5, carried on respective shafts S7,and each Yof the rst six shafts in sequence from the left end has twosprockets 88 xed with respect thereto,vone sprocketto receive a drivechain from the` next preceding driving element, and the other sprocketto drive the next succeeding element.V

The roller drive (Figs. 5, 6 and 8, and appropriate Sectional views) isfrom motor S9 through shaft 90, coupling 91, gear reduction unit 92,chain 93,V sprocket 94 (Fig. 13) pinned to shaft 95, sprocket 96 alsolpinned to shaft 95,chain 97, sprocket 98 on roller shaft 87, sprocket 99on kroller shaft 87, chain dtto sprocket V103i on the next roller shaft87a (Figs. 5 and 14) and so on as farjas the second last roller shaft87h which is driven by chain 102 from the preceding Vroller shaft, Vbutdoes not transmit the drive further. The last roller shaft 87e (Fig. 15)is an idler shaft carrying roller 61a for a suit- Y able purpose whichwill appear later.

` When motor 89 is energized, it causes all rollers 61 to rotate in adirection calculated to advance to the right, a rod4 carried thereon.Assume that the carriage 29 has beenmoved so that its leading .end isapproximately in the position indicated Vby the broken line `showingwithin mill 20 (Fig. 2). .Motor "62 is then stopped and motor 89 isstarted. All rollers move clockwiseY (Figs. 2 and 6) andthe rod'moves tothe right with its leading end progressively' assuming an increasingoverhang with respectto the leading end of the carriage.V As the rodscenter of gravity clears the end of the carriage and the rod tips asshown in Figt 2, being now supported only by idler roll 61a, the leadingend ofthe rod slides to contact with the mill bottom (or with the millload of ore and rods). Thecarriage can now be withdrawn, idler` rolltravelling rearwardly Von' the rods surface until the rod drops clear ofthe carriage and lies in the mill. The carriage continues to moverearwardly to its original position in engagement with the loadingyrack.

The safety locksv I show in Figs. 4, 6, 9 and 16 aisafety locking devicewhich serves two functions, namely it secures the rear end of thecharging apparatus (left end in Fig. 6) to the platform, to preventtipping, and it insures that the apparatus .cannot be operated until itAis secured in properly aligned position with respectfto the rodAlthough :drireix axle @arefrredm in the lastprecediris paragraph .thereare 1W? .Such locking devices, vthe" are v.identical il;

structure and function, and only one will`be described in detail. Y n

On the 'external face of a rear leg 38 are two horizontal lugs 105v and,106 which combine with the foot 38a and a headplate 107 to align andsupport a plunger 108. I hisplunger is vertically movable in a guidesleeve 109 lxedV in suitable apertures in members v105, 106 and 38a.Fixed on plunger 108 is a suitable split cam bushing j110 which, whenthe cooperating parts thereof are in operative contact (Fig. 9)Y and theplunger is rotated bycan operating arm 111, causes limited upwardmovement of the plunger.

At its-lower. end the plunger has a small crosspiece 114 which can beturned, by rotation of the plunger, so that a linger of the crosspiecemoves beneath a flange of the platform-supporting I-beam 36 to firmlylock the charging device tothe platform. Rotation of the plungerthrough'90 degrees around its vertical axis permits the crosspiece 114to be aligned with a suitably oriented slot 115 in foot 38a and anotherslot 109a in sleeve 109, so that the plunger may be raised from thelocked position of Fig. 9 to the unlocked position of Fig. 16.

ln head plate 107 is a slot 116 (Figs. 4, 9 and 16) which permits upwardmovement therethrough of a tab or vane 117 on top of the plunger. Whencrosspiece 114 is in' unlocked position, the tab slot 116 is properlyorientedV to permit tab 117 to pass through it to the position of Fig.16. Tabs 117V are used for attachment thereto of the hooks on a chainsling as will hereinafter appear. The hooks cannot engagethe tabs untilcrosspiece 114 is raised above the oor plate.

The safety switches Referring to Fig. 9 I show a safety switch 118having an operating plunger engageable by a camming iinger 119 onplunger 108 when the plunger is down and turned to locking position. Theswitch arrangement is such that when the charging mechanismris placed inoriented posi.- tion with respect to the rod mill, and manipulating arms111 are turned to render the mechanism immovable, iin'- gers 119simultaneously turn to operate plungers 118 and close the contacts ofswitches 108, which in conjunction with other controlswitchdevicespermits energize tionl ofthe various movable parts heretofore described.

The wiring diagram kand operation Referring now `to the wiring diagram,Fig. 18, it will be noted that certainY mechanical elements orassemblies are shown schematically.

The carriage motor `62 is reversible depending on actuation `either ofthe forward switch SF or the1 reverse switch"SR,'each of which is`Vresponsive, respectively, to ener'gization of the coils v131 and 148when forward butvllnergizatio'n of coil 131 starts motor 62 and the carriage moves towards the right. When it arrives in unloading position, itmoves limit switch 128` from its a positionrto its b position, therebybreaking the circuit to motor 62, which stops.

Y The operator now closes the charging button 127, so called because itinitiates operation of motor 89 to move the bar to charging or unloadingposition, as follows: From L1 through conductor 140, switch coil 141(which closes switch 142 whenY energized), conductor 143 to button 127,and through conductor 144 to switch 128, now

in b position, and thence through conductors 145 and 134, closed safetyswitch 118, conductor 135, closed safety switch 118, conductors 136 and137 to L3.

Motor switch 142 closes the circuit to `motor 89 which advances the barto a position in which its center of gravity overhangs the carriage andthe bar drops until its leading end reaches the mill oor, or the loadtherein. The operator then withdraws the carriage by depressing carriagereverse button 126 to close the following circuit: From L1 throughconductor 147, reverse switch coil 148 (which closes reverse switch SR),conductor 149 to button 126, and conductor 150, limit switch 129 inclosed position, conductor 151, safety switch 118, conductor 135, safetyswitch 118, conductors 136 and 137 to L3. Motor 62 nowruns in reverse,`movingrthe carriage 37 to the left until it breaks the just-describedmotor circuit by opening limit switch 129.

This completes an operating cycle.

The limit switches 129 and 128 are xed in suitable positions on eitherthe frame or carriage in such a way that they can be opened by anintercepting nger during movement ofthe carriage relative to the frame.The forward and reverse switches SF and SR for motor 62 are biased toopen position, but are closed by energization' of their respective coils131 and 148 in the manner described. The switch 142 for motor 89 islikewise biased to .open position, but is closed by energization of coil141. Quite obviously the circuit shown ton 125 orr reverse button 126are depressed. In the diagram cam fingers 119, heretofore described, arein unlocked positionv and therefore safety switches 118 are open. Limitswitch 129 is in open position becausecit has been opened b'y travelioflcarriage 37 to its extreme leftor loading position. Limit switch128 isa'double pole' double throw switch 'having an a position to which it isnormally biased, and b position to which itcan be moved by the carriageas will appear. A switch 127is provided for motor 89 for operating therollers 61.

AssumeV that the charging device has beenset in place and the frame 37is locked to the floor as previously de isamerely one simplifiedembodiment of a suitable electrical control system.

. As a result ofthe disposition and manner of operation of the safetyswitches 118, these switches cannot normally lbe lclosed exceptv byplacing the plunger 108V in locked position. This means that thecarriage .can' not be moved in its frame except Ywhen the frame isproperly positioned and aligned. c j

,When the plunger V108 is in raised (unlocked) posi tion,'as shown inFig. 16, vane 117 has anvaperture 117a which permits insertion of a hooksuspended Yfromr atravellingcrane. -At the Vrear end of the frameuis apair of spaced lugsl 157 (Figs. 4 and 6) which are similarly perforatedVfor' lconnecting means.- The as-` sembled frame ,and carriage, whenunlocked, can be picked up by an overhead crane and carried to a newworking location adjacent tocanother rod mill. A similarly perforatedplatform or other xedanchoring means receives the frame at all neededlocations.

While the charging means hereinabove described has beenshown anddiscussed in connection with the loading of rods into a rod mill, it isquite apparent that the essential advantages of the invention may beachieved in other applications wherein `elongated elements must becharged into a relatively inaccessible hollow enclosure having acharging door or opening in the end thereof.

What I claim is: Y v

' 1."Apparatus of the character described for charging an elongatedarticle horizontally through an aperture in thefend wall of anenclosure, said apparatus comprising a frame,v said frame having a pairof spaced parallel tracks extending towards said aperture, anarticle-carrying carriage having wheels movable on said tracks wherebytopermita leading portion of said carriage to be extended through saidaperture to an article-unloading position within said enclosure, saidcarriage havingA .when Vsaid carriage portion has been'extended throughsaid aperture to said unloading position, and for continuing suchrotation until the centerV of' gravity of said article is moved inwardlybeyond the'innermost roller, and means for thereupon `withdrawing saidsaid enclosure; Y Y

2. Apparatus as deiined in claim 1 wherein reversible motor means isprovided, carried on said carriage for moving said carriage from aloading position entirely outside of said enclosure, .to'ran unloadingposition partially withinY said enclosure. v

V3. Apparatus as defined inV claiin l wherein means is provided forautomatically` stopping said carriage when it reaches unloadingposition. Y

4. Apparatus as dennedV in claim 2 wherein limit stop means is providedfor automatically stopping-said'carriage at a predetermined point, bothat its loading posi-Y tion and at its unloading position.

5.Y Apparatus of the character described'for charging anelong'atedarticle horizontallyV through an aperture in the end wall of anenclosure, said'apparatus' comprising a supportingrfrarne having a pairof spaced parallel Y tracks extending towards vsaid aperture, anarticle-carry- L ing carriage having wheelsV movable on said trackswhereby to permit a leading portion-of VsaidV carriage for energizingsaid motor, said motor being operatively i* eifectiveron s aidrcarriageto cause pre-selected forward or return movement thereof. Y 1 6.Apparatus of the character-describedfor .charging an elongated articlehorizontallylthrough'an* aperture in the end wall of an enclosure, saidyapparatus comprising Va supporting lframe having aV pair Vof spacedvparallel tracks extendingtowards said aperture, an article-carrywherebyto permit a leading portion Vofsaidcarriage to* be "ext-ended throughVsaid aperture tQ- 'article-unloading `position within said enclosnrefand to be"returnedftoY an article-loading position outside-' said iaperture/said Y Ycarriage,havingajseries of rollers "disposed-n t osupport` isaidYarticle vduringrmo'ven'ient ofV 'said-carriage andltoVunload said article atunloading -positionfaiirstelectricV motor anda'iirst electric circuit forV energiZation-of 'said iirst motor, saidiirstrnotor being operatively effective on said carriage to causeVselectedforward or return movement thereof when said circuit iscompleted, and aY second electric motoranda second electric circuit forvenergization of. said Asecondmotor, saidfsecondV motorV beingVvoperatively enective `on 'said rollers Vtoprodu'cce article-unloadingVrotation vthereof when said carriage is moved to Yunloading position.,Vf Y V.7..Apparatus of the character described-for charging anelongated'afrticle horizontally through' an aperture'in the end wall oanenclosure, said apparatus comprisi carriageV from energizing saidfmotor,'rneans establishin"gV :anfe'pe'rativ'e Y motor. y

` i0. Apparatus as defined in claim 7 wherein the roller linkagebetweenbsaid first motor and said carriage whereby to advance or retractsaid carriage betweenvsaid loading and unloading positions; a-se'con'ci`electric motor and a second electric circuit for energizing `said secondmotor, means establishing an `Voperative linkage' between said secondmotor and said rollers( to produce unloading rotation Vof said rollerswhen fdesired, said supporting frame being vtransportable into `randout-of working posi- Ytion in alignment with said aperture, movablemeans for loeking said-frame in` said Working position, normally opensafetyswitch means in series Lin said first-'circuit, and meansoperatively responsive to-locking movement of said locking'means andeffective,` upon such locking movement, to closeV said safety switchmeans whereby saidvfirst motor is energizable only when said supportingframe Ais locked inlworking position.

8. ApparatusV as defined inV claim 7 wherein limit switch means Visprovided in said first circuit, said limiti switch means being effectiveto interruptV said rst circircuit and Astop Ymovement ofsaid carriagewhen it reaches a predetermined limit of travel in either direction.

9. Apparatus as defined in claim 8 wherein said safety switch means andsaidA limit switch fmeans are disposed in series Ain said tirst electric'circuit so that opening of either the safetyswitch means or the limitv'switch means renders said first circuit ineffective to energize saidlirst adjacent the leading endv ofgthe carriage is an idler roller, andthe rest of the rollers are driven by said second motor.v Y Y i il.Apparatus as' defined 'in' claim'7 whereinsaid supporting frame Visprovided with a second pair of Vspaced parallel tracks extending towards.said aperture, and the end of said carriage remote Vfrom said enclosureis Ypro'- vided with a 'pair of wheels in rolling contact with the kingycarriage having wheelsV movable on' said tracks lower faces of saidsecondipair of tracks.'

' l2. Apparatus of the Ycharacter described forgcharging an`elongatedarticleV horizontallythrough anY aperture in the. end wall ofan .Y enclosure, said apparatus comprising a supporting frame Yhaving apairr'rof Vspaced parallel tracks extending` towards said aperture, anvarticle-v'Y carrying carriage having WhjeeIsmQYable-onsad tracks Ywhereby to permit a leading' portican' of said"carriage to Y Ybeextended through said aperture .to 4an article-unloading Y positionwithin said apertureand'to'rbefreturnedfto an Aarticle-loading positionoutside isaidaaperturegsaid carriage having a seriesof1rollers kiisposedto support lsaid article duringV movementv of :said carriageVto-.nloading' positionl and to unload said article. at runloadingposition, an electric motor and anselectriccircuit kforzener'gizing saidmotor, saidimotor being operatively effected-on said ingVapsupportingifraxne having a 'pair of spaced'paiallei Vtracks'extencringtowards said aperture-an article-carrying'carriage having wheelsmovableV on said Vtracks whereby to permit va leading portionofsaid'carriage to Vbe extended through said VapertureYto',anarticle-unload- `ing positionwwithin said aperture'` and tobegreturned to Van 'article-loading position-outsidesaid apertl'lre,vsaid carriage to cause pre-selected forward orreturn movement thereof,said V4supporting :frame Vbeing ytransferable into-'and out of 1aWorking position'fin i alignment with saidaperture, movable means Vforlocking said franiein VVsaid working position, normally open safetyswitch =means in series Ain said circuit, and meansoperativelyresponsive to lockingmovement of said locking means anderfective, uponsuch locking movement, ,to .close said safetyswitch means wherebyV saidmotor is .energizable only when said supporting frame is locked inworking'position. v

References Cited Ain ofthis patent `UNITED VSTATES .PA'rniSI'l's'V i'

